111
FXUS65 KCYS 221210
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
610 AM MDT Sun Sep 22 2024

.KEY MESSAGES...

- Near freezing temperatures are possible in some low-lying and
  wind sheltered areas through early this morning and again
  Sunday night. A Frost Advisory is effect for Converse and
  Niobrara counties tonight.

- Above average temperatures and dry conditions expected for the
  middle of the work week, with increased chances for critical
  to near-critical fire weather conditions Wednesday onward.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 300 AM MDT Sun Sep 22 2024

Rain showers and isolated thunderstorms remain south of our cwa
border early this morning. The wrap around moisture and upslope
flow should keep cloud cover in the region through mid morning,
especially the I-80 corridor from The I-80 Summit to Cheyenne
County. Mostly clear skies further to the north have allowed
temperatures to decrease quickly, with several areas in the
valley regions and northern forecast zones in the low to middle
30s. A few areas have even decreased to the upper 20s. This
most likely will allow for patchy frost to occur, especially in
the Niobrara and Converse County areas where a Frost Advisory
is in effect through 8am MDT. Additionally, the upslope flow and
cooling temperatures are likely to create patchy, dense fog
over the I-80 Summit. Have gone with a Dense Fog Advisory to be
prudent. Main timeline of concerns will be 12-14Z, but have
given a 1 hour buffer on the front end and back end of the
headline as a precaution. Cool temperatures will persist across
the majority of the cwa, but have bumped up temperatures a
couple more degrees because of the cloud cover expected to push
south and east slightly more quickly by this afternoon. Overall,
still expect temperatures to be in the 60s to low 70s. Slightly
cooler in the 40s/50s for the mountain zones.

The start of Monday will bring patchy frost once again to valley
regions across our cwa. Morning lows in the upper 30s to low 40s
will make it feel chilly outside to start the week. Warmer
temperatures and dry conditions are expected for Monday and
Tuesday afternoon however. Daytime highs will range from the
low 70s to low 80s for Monday, and slightly cooler temperatures
on Tuesday. We will be on the periphery of a passing cool front,
that will likely not bring any precipitation. Seasonal
temperatures should make for a pleasant start to the first week
of fall across southeast WY and western NE.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Issued at 300 AM MDT Sun Sep 22 2024


By the middle of this week, an upper level ridge will be positioned
over the central Rockies as 500mb heights climb above 588 dam (near
climatological 90th percentile) with the ridge axis extends well
north of the Canadian border. This will support warmer and drier
weather from mid-week headed into next weekend. Thursday still looks
to be the warmest day with afternoon highs up to 80F west of the
Laramie Range and mid-80s, possibly near 90F, east of I-25 into the
NE panhandle. An upper level shortwave will pass well to the north
Thursday that will begin to gradually knock down 700mb temps through
the remainder of the week, but temperatures will remain above normal
for late September headed into next weekend. Additionally, this
system will bring gusty winds to our area with portions of the
Laramie Range gusting 30-40 mph Thursday afternoon, but high winds
are not expected. Looking at cluster analysis, a slightly cooler
solution exists for late this week if the closed low remains
stationed west of the Ohio River valley, but this solution is only
supported by >10% of the grand ensemble.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 606 AM MDT Sun Sep 22 2024

Mostly VFR conditions across area terminals with mid-to-low
level clouds associated with the system down in CO this morning.
Currently, KCYS is reporting MVFR ceilings with southerly
upslope flow that will remain through mid-morning. Latest HREF
guidances suggests there could be a quick break in low clouds,
but overall should remain before clearing around 16-17z. Skies
will continue to clear throughout the afternoon into this
evening.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Frost Advisory until 8 AM MDT this morning for WYZ101-102.
     Dense Fog Advisory until 9 AM MDT this morning for WYZ116.
NE...None.

&&

$$

SHORT TERM...BW
LONG TERM...MB
AVIATION...MB